The present disclosure relates generally to gas analysis and, more particularly, to systems and methods for measuring gas flux.
The increasing concentrations of carbon dioxide and other traces gases (e.g., H2O, CH4, N2O, NH3, etc.) in the atmosphere, and the resulting greenhouse effect and climate change, have become important topics for scientific research. In order to understand the global carbon balance, it is necessary to determine the rate at which carbon dioxide and energy exchanges between the atmosphere and terrestrial and oceanic ecosystems. The air within a few hundred meters above the earth's surface is mostly turbulent, so that turbulent structures (e.g., vortices of variable sizes) called “eddies” are responsible for the vertical transport of most of the gases, including carbon dioxide and water vapor, and also heat and momentum between the surface and the atmosphere. The rates of such transport can be calculated from simultaneous, high-frequency measurements of the vertical component of wind speed, the concentrations of carbon dioxide and water vapor, and the air temperature. Similar calculations can be made to measure methane or other gases of interest, for example.
One issue involved in computing turbulent gas flux rates is that multiple measurement devices are used to provide the necessary data, including gas analyzers, temperature sensors, wind speed measuring devices, and/or water vapor analyzers, among others. Each of these measurement devices operates on its own clock. In order to properly compute turbulent gas flux rates, the clocks of the different measurement devices used for accumulating data should be synchronized.
In one conventional approach, analog measurement data is transmitted to a data logger that logs the data and then samples the analog data. However, not all measurement devices provide analog outputs.
Another conventional approach provides for a synchronous bus between the measurement devices that synchronizes the clocks of the multiple measurement devices. The main problem with synchronous buses is that they do not scale well. Also, synchronous buses tend to be proprietary to each manufacturer.
Also, in many conventional approaches, the measurement devices and any other devices at the sampling site do not offer any processing or analysis of the raw data. Data is collected over a period of time, for example over two weeks, and is stored at the sampling site, typically in a storage device coupled to or included in one of the measurement devices. A scientist must then go out to the sampling site to retrieve the data on the storage device for analysis. This conventional approach is very cumbersome since going to the sampling site on a repeated basis is tedious and time consuming, and can be dangerous if the sampling is being performed in remote or difficult-to-access locations.
Accordingly, it is desirable to provide systems and methods that overcome the above and other limitations of conventional approaches to measuring gas flux.